Cutoff devices with a perforated valve seat wall located in a housing between intake and discharge, as well as a closure strip of elastic material that is applied against the valve seat wall by the through-flow pressure and that can be wound onto the wall are known in principle. Here, the closure strip is clamped on one front side, on the housing or the valve seat wall, while its other front side is disposed on a rotatably borne actuating shaft in the housing at a distance from the valve seat wall. Since the actuating shaft is disposed opposite the clamping point of the closure strip, the closure strip in its closed position forms a U-shaped loop whose height diminishes as the winding of the closure strip from the valve seat wall progresses, and thereby reduces the opening of the cutoff device. The winding or opening is effected by turning the actuating shaft, by means of an external hand wheel (see German Pat. No. 897,639).
Although cutoff devices with a flexible closure strip would be superior to the usual valves, cocks and slides, especially because of the slight amount of actuating force that is required and their practically unlimited opening characteristics, they could not be used heretofore in practice because the long loop of the closure strip fluttered, from the influence of the medium flowing past it, and this resulted first in tears on the long edge of the strip, which eventually could lead to destruction of the strip.
For this reason, the problem is to produce a cutoff device of the type that has been described, such that the damage to the strip will be avoided.